Recently, several experiments have forced the community to reexamine widely accepted beliefs about this fascinating material. NMR measurements revealed that \(\mathrm {Sr}_{2}\mathrm {Ru}\mathrm {O}_{4}\)  is in fact a singlet superconductor [1]}, [2]}, [3]}. Applying uniaxial strain leads to a separate onset of superconductivity at \(T_c\)  and of time-reversal symmetry breaking (TRSB) at \(T_{{\scriptscriptstyle \mathrm {TRSB}}}\)  [4]}. Combined with the observed jump of certain elastic constants across \(T_c\)  [5]}, [6]}, these observations have led to the proposal that \(\mathrm {Sr}_{2}\mathrm {Ru}\mathrm {O}_{4}\)  is a two-component singlet superconductor, with \(T_{{\scriptscriptstyle \mathrm {TRSB}}}\)  signalling the condensation of the second component [7]}, [8]}, [9]}, [10]}, [11]}, [12]}. Meanwhile, there is no indication of a heat capacity anomaly at \(T_{{\scriptscriptstyle \mathrm {TRSB}}}\)  [13]}, in contrast to the sharp jump seen at \(T_c\) . More generally, there is no experimental evidence that time-reversal symmetry breaking is a bulk effect—in fact, muon spin rotation (\(\mu \) SR) experiments find variations of the effect for distinct samples and signatures consistent with diluted magnetic moments [4]}. This calls into question the widely accepted view that \(\mathrm {Sr}_{2}\mathrm {Ru}\mathrm {O}_{4}\)  is a multi-component superconductor.
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